Ringing propeller/shaft

[tph]

Boat: 1989 PS 190/351 Indmar 1:1 velvet drive.

I added a TT rudder and had my 3 blade 13 x 13 legend prop rebuilt over the winter. We used the boat for the first time a week ago. Between 600 and 1100 RPM there is a high pitched ringing sound coming from the prop shaft.

I have disconnected the shaft from the transmission to make sure it wasn't the transmission. I have also checked the seal packing and aligned the shaft. There is no noise when it is run on the trailer. The boat runs great but the ringing is annoying. Has anyone had any experience with this? Any help would be greatly appreciated. Thanks

[bigmac]

Shaft bushing? Seems the most likely given what you've already checked, and assuming that it happens only in gear.

[tph]

I've replaced the shaft bushings, repacked the shaft packing, and realigned the engine/shaft. You can easily turn the prop with one finger. But, when i put it in forward gear it still rings. (like a wet finger on the rim of a wine glass) It occured to me that the shaft is being pushed forward into the drivetrain when in gear and that maybe it is causing two parts to contact each other and ring. Does anyone here know enough about the anatomy of a velvet drive/damper plate assembly to offer suggestions? Thanks in advance for any help.

[FrankSchwab]

I'd guess the Prop is vibrating, and the vibrations are being conducted up the drive shaft. I'd swap to another prop (borrow one if you have to) and see if the ringing changes.

Alternatively, it could be a resonance in the new rudder. Swap the old one back to see if the noise goes away, or put your finger/ear to the rudder shaft at 1000 rpm and see if its singing.


/frank

I'd appreciate knowing if a sloution to the ringing has been found. I have a sailboat with a 13 HP Westerbeke (2:1 transmission gearing) which rings between 1200 and 2000 RPM (600 to 1000 prop shaft RPM), only when in forward gear. The cutlass bearing is fairly snug, and I haven't been able to find the cause of the ringing yet. The prop is 2 blade, brass.

[sully]

I have had this happen to me before, it usually been on "new" props. I have just taken my prop back to the prop shop explained what has happened and what RPM and gotten in back good as new good. I believe they take some of the sharpness out of the edge.

[tph]

Originally Posted by sully

I have had this happen to me before, it usually been on "new" props. I have just taken my prop back to the prop shop explained what has happened and what RPM and gotten in back good as new good. I believe they take some of the sharpness out of the edge.

That was the resolution to my problem. I took a flat file to the blade edges making them square to the propulsion surface and the ringing stopped.